Scheduling of beamformed data to reduce interference

ABSTRACT

A system and method are disclosed for coordinating the scheduling of beamformed data to reduce interference in a wireless system. A customer premise equipment (CPE) uses a plurality of bits to quantize the phase angle of the beamformed data received by CPE and reports it to its serving base station. The serving base station selects one of the phase adjustment angles based on the bits received from the CPE in order to schedule the data transmission to the CPE. The phase adjustment angles are in “n” degree steps.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 61/362,659, filed Jul. 8, 2010, and is related to U.S.Provisional Application No. 61/329,504, filed Apr. 29, 2010, which isincorporated herein by reference. Both these applications areincorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention generally relates to systems and methods forcoordinating the scheduling of beamformed data to reduce interference.Transmissions from a base station can be scheduled according to avariety of factors, including the level of interference from adjacentbase stations, a priority of reducing interference, and the relativephase differences of adjacent base stations, leading to lowerinterference levels and to generally higher network efficiency.

Wireless communications systems can use transmit beamforming to improvethe level of the signal seen at a desired receiver, as well as to reducethe levels of interference seen at other receivers. The interferencereduction capability of beamforming can be advantageous in cellularwireless systems, where high levels of interference can severely reducethe capacity of such systems.

Beamforming generally refers to techniques used in wirelesscommunications systems such as radio frequency, optical frequency oracoustic frequency systems wherein signals transmitted or received bymultiple transmit or receive sensors are combined in such as way as toimprove their overall gain, or carrier to interference ratio.Beamforming uses at least two transmit or receive sensors.

Beamforming has typically been used in cellular wireless communicationssystems to improve the range over which a mobile device can communicatewith the base station. An additional possibility with beamforming is theability to reduce interference by choosing phases and signal amplitudesthat can cause the signals, received at or transmitted by a differentmobile station, to cancel.

Beamforming typically employs multiple antennas at the base station anduses signal processing techniques to ensure that the phases of thesignals are aligned with each other by the time that they reach themobile device. In systems that use Time Division Duplexing (TDD), wherethe same set of frequencies are used for both downlink (base station tomobile station) and uplink (mobile station to base station)transmissions, the base station can take advantage of the channelreciprocity to adjust the amplitudes and phases of the transmissions ateach antenna. For Frequency Division Duplexing (FDD) systems, wheredifferent frequencies are used for the downlink and uplinktransmissions, feedback from the mobile station to the base stationabout the amplitudes and phases of the signals received at the mobilestation is generally required.

Cellular wireless beamforming systems typically use two to eightantennas. Since the cost of supporting beamforming in a base stationproduct increases as the number of antennas increase, systems with morethan eight antennas have generally been regarded as being costprohibitive.

FIG. 1 illustrates a wireless beamforming system 100 that uses twotransmit antennas at a base station to communicate with a mobile station108 in accordance with an embodiment of the invention. Signal processingalgorithms at the base station 102 choose the appropriate phases andamplitudes of the signals 104 and 106 at each of the base stationtransmit antennas to ensure that the combined signal received at themobile station 108 has sufficient power to operate correctly.

FIGS. 2-5 show some examples of how the phase and amplitude differencesbetween the two signals 104 and 106 arriving at a mobile device (e.g.,108), or a customer premise equipment (CPE), can impact the combinedsignal that the receiver sees. A beamforming system (e.g., 100) cancontrol the relative amplitudes and phases at the transmitter so thatthe combined signal seen at the receiver (e.g., 108) can have increasedamplitude, or can have reduced amplitude.

FIGS. 2A and 2B illustrate plots 202 and 204, respectively, where twosinusoidal signals of equal power with phase differences of 0° and 180°are being received at a mobile device (e.g., 108) in accordance with anembodiment of the present invention. In the first plot 202, the twosignals 104 and 106 are perfectly aligned with each other in phase. Thecombined signal (marked with triangles) has twice the amplitude of theindividual signals. Referring to FIG. 2B, in the second plot 204, thetwo signals are 180° out of phase with each other. In this case, thesignals cancel each other out perfectly, resulting in a combined signalthat has zero amplitude. The receiver (e.g., 108) in this case does notdetect any signal due to the perfect cancellation of the signals throughdestructive interference.

FIGS. 3A and 3B illustrate plots 302 and 304, respectively, where twosinusoidal signals of unequal power with phase differences of 0° and180° are being received at a mobile device (e.g., 108) in accordancewith an embodiment of the present invention. In this example, the twosignals are not equal in power but rather the first signal 104 is 3 dBstronger than the second signal 106. Referring to FIG. 3A, the firstplot 302 depicts the two signals 104 and 106 perfectly aligned with eachother in phase, resulting in a much stronger received combined signal.The second plot 304 shows the scenario where the two signals 104 and 106are 180° out of phase with each other. In this scenario, the signals donot completely cancel each other out, but the combined signal at thereceiver is still attenuated significantly when compared with the caseof the two separate signals being aligned perfectly with each other(e.g., in plots 202 and 302 of FIGS. 2A and 3A, respectively).

It is not necessary that the signals arriving at the receiver be alignedexactly in phase in order for a combining gain in signal strength to beachieved. Likewise, it is not necessary that the signals be exactly 180°out of phase with each other to realize a signal cancellation. Thus,FIGS. 4A and 4B illustrate plots 402 and 404, respectively, where twosinusoidal signals of unequal power with phase differences of 45° and160° are being received at a mobile device (e.g., 108) in accordancewith an embodiment of the present invention

FIGS. 4A and 4B, respectively, show the same two signals (e.g., signals104 and 106) with the same 3 dB power difference as in FIGS. 3A and 3B,but this time the phase differences at the receiver (e.g., 108) are 45°and 160°. In the scenario, where the signals are received with a 45°phase difference (i.e., in plot 402), the combined signal at thereceiver still shows significant gain and is not much reduced whencompared to the scenario where the signals are received with a 0° phasedifference, as shown in plot 302 of FIG. 3A. Similarly, when theoriginal signals are received 160° out of phase with each other (asdepicted in plot 404), there is still a significant reduction in thelevel of the combined signal when compared to the scenario where thesignals are received with a 180° phase difference shown, as shown inplot 304 of FIG. 3B.

FIG. 5 illustrates a plot 500 of the power gain of the combined signals,also known as the beamforming gain, versus the phase difference of twosignals (e.g., signals 104 and 106) at a receiver (e.g., 108) inaccordance with an embodiment of the present invention. Note that theplot 500 assumes that both signals are received with equal amplitude,similar to the signals depicted in FIGS. 2A and 2B. The beamforming gainis relative to a signal sent at a nominal level of 0 dB from one of thetransmit antennas. The largest gain (6 dB) is seen when the two signalsare perfectly aligned in phase (e.g., as in plot 202), while the lowestgain (in this case negative ∞ when expressed in dB) is seen when thesignals have a phase difference of 180° (e.g., as in plot 204).

Modern wireless communication networks include many different networktopologies comprising heterogeneous mixtures of macrocell, microcell,picocell, and femtocell resources. At the highest level of wirelesscoverage, a macrocell provides cellular service for a relatively largephysical area, often in areas where network traffic densities are low.In more dense traffic areas, a macrocell may act as an overarchingservice provider, primarily responsible for providing continuity forservice area gaps between smaller network cells. In areas of increasedtraffic density, microcells are often utilized to add network capacityand to improve signal quality for smaller physical areas where increasedbandwidth is required. Numerous picocells and femtocells generally addto network capacity for even smaller physical areas in highly populatedmetropolitan and residential regions of a larger data communicationsnetwork.

This mixture of larger and smaller cells can reduce periods of networkcongestion created by traditional network architecture which previouslybottlenecked a majority of regional subscriber communications through asmall number of larger network cells (e.g., macrocells or microcells).This congestion reducing technique can improve a service providernetwork's Quality of Service (QOS) as well as network servicesubscribers' collective Quality of Experience (QOE) within a particularportion of a data communications network. Negative effects associatedwith poor QOS and poor QOE (e.g., conditions largely caused bycongestion and/or interference), which can be mitigated by adding asubstantial number of short-range wireless base station devices tonetwork infrastructure, may include: queuing delay, data loss, as wellas blocking of new and existing network connections for certain networksubscribers.

As the number of overlapping cells in a network increases (i.e., thenumber of macrocells, microcells, picocells, and femtocells in anetwork), it becomes increasingly important to manage the airlinkresources shared by the components in a network. By way of example,resources such as frequency channels, timeslots, and spreading codesneed to be managed for each cell in a network, and poor management canresult in increased interference and a decrease in overall networkefficiency.

Conventional systems have attempted to use beamforming techniques tomanage a transmission from a base station to an intended mobile deviceto increase the signal strength similar to the techniques described inplots 202, 302, and 402. Some conventional systems have attempted toreduce undesired interference levels using beamforming signalcancellation techniques similar to the techniques described in plots204, 304, and 404. However, these systems require relatively complexsignal processing algorithms and communications between base stations toachieve the interference reductions. Thus, it would be desirable toschedule transmissions in a wireless network such that the signalsreceived by a mobile device from a serving base station combine in aconstructive manner at the mobile receiver, while signals arriving at amobile base station from non-serving base stations combine in adestructive manner at the mobile receiver. Additionally, it would bedesirable for the scheduling to be minimally resource-intensive so thatcomplex scheduling can be easily performed.

SUMMARY OF THE INVENTION

The present invention generally relates to systems and methods forcoordinating the scheduling of beamformed data to reduce interference. Acustomer premise equipment (CPE) uses a plurality of bits to quantizethe phase angle of the beamformed data received by the CPE and reportsit to its serving base station. The serving base station selects one ofthe phase adjustment angles based on the bits received from the CPE inorder to schedule the data transmission to the CPE. The phase adjustmentangles are in “n” degree steps. In an embodiment, two bits are used toquantize the phase angle reported by CPEs to their serving base stationsand four phase adjustments angles (i.e., in 90 degree steps) are used.The two bit allows the phase zones to be quantized into four differentlevels. Each phase angle adjustment is mapped to a single phase angledifference.

In an embodiment, three bits are used to quantize the phase anglereported by CPEs to their serving base stations and four phaseadjustments angles (i.e., in 90 degree steps) are used. The three bitsallow the phase zones to be quantized into eight different levelsinstead of four. Each phase angle adjustment is mapped to two phaseangle differences. The additional quantization bit is used todifferentiate between the second most optimal phase angle correction andthe third most optimal phase angle correction.

In an embodiment, a computer implemented method for transmittingbeamformed data to a mobile station includes receiving a quantized phaseangle information of a reference signal from a mobile station at a firstbase station that transmitted the reference signal to the mobilestation. A first phase adjustment angle is selected based on thequantized phase angle information received from the mobile station. Afirst beamformed signal that is provided with the first phase adjustmentangle based on the received quantized phase angle information istransmitted to the mobile station from the first base station. Thereference signal may or may not be a beamformed signal.

In an embodiment, the first base station is a serving base station forthe mobile station, and the mobile station is receiving an interferencesignal from a second base station. The interference signal may or maynot be a beamformed signal. The first beamformed signal is transmittedto the mobile station by the first base station as part of a first datapackage. The first data package in a first wireless resource isscheduled with the first phase adjustment at the first base station incoordination with an associated second phase adjustment of a secondwireless resource at the second base station.

In an embodiment, a computer implemented method for receiving beamformeddata from a base station includes receiving a first signal from a firstbase station at a mobile station. A first phase difference of the firstsignal is measured at the mobile station. A quantized phase angleinformation of the first signal is transmitted by a mobile station to afirst base station that transmitted the first signal to the mobilestation. A first beamformed signal that is provided with a first phaseadjustment angle is received from the first base station. The firstphase adjustment angle is selected by the first base station based onthe quantized phase angle information transmitted by the mobile station.The first signal may or may not be a beamformed signal.

In another embodiment, a wireless communication system is provided at abase station for coordinating the scheduling of beamformed data toreduce interference. The system includes a processor; a receiver; and atransmitter. The system is configured to: transmit a first signal to amobile station, receive a quantized phase angle information of the firstsignal from the mobile station, select a first phase adjustment anglebased on the received quantized phase angle information from the mobilestation, and transmit a first beamformed signal that is provided withthe first phase adjustment angle based on the received quantized phaseangle information to the mobile station. The first signal may or may notbe a beamformed signal.

In yet another embodiment, a wireless communication system forcoordinating the scheduling of beamformed data to reduce interferenceincludes a first base station; a second base station; a datacommunication network facilitating data communication amongst the firstbase station and the second base station; and a first mobile station. Afirst beamformed signal received by the first mobile station from thefirst base station is received as a communication. A second beamformedsignal received by the first mobile station from the second base stationis received as interference. The system is configured to: transmit afirst signal to a mobile station, receive a quantized phase angleinformation of the first signal from the mobile station, select a firstphase adjustment angle based on the received quantized phase angleinformation from the mobile station, and transmit a first beamformedsignal that is provided with the first phase adjustment angle based onthe received quantized phase angle information to the mobile station.The first signal may or may not be a beamformed signal.

The present invention may further include a computer readable mediumencoded with computer-executable instructions for coordinatingbeamformed data for wireless transmission, which when executed, performsa method comprising: scheduling a first data package in a first wirelessresource with a first phase adjustment at a first base station incoordination with an associated second phase adjustment of a secondwireless resource at a second base station; and transmitting the firstdata package as a first beamformed signal to a first mobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described in detail below byway of example and with reference to the accompanying drawings, inwhich:

FIG. 1 illustrates a wireless beamforming system that uses two transmitantennas at a base station to communicate with a mobile station inaccordance with an embodiment of the present invention;

FIGS. 2A and 2B illustrate two sinusoidal signals of equal power withphase differences of 0° and 180° being received at a mobile device inaccordance with an embodiment of the present invention;

FIGS. 3A and 3B illustrate two sinusoidal signals of unequal power withphase differences of 0° and 180° being received at a mobile device inaccordance with an embodiment of the present invention;

FIGS. 4A and 4B illustrate two sinusoidal signals of unequal power withphase differences of 45° and 160° being received at a mobile device inaccordance with an embodiment of the present invention;

FIG. 5 illustrates a plot of the power gain of the combined signals,i.e. the beamforming gain, versus the phase difference of two signals ata receiver in accordance with an embodiment of the present invention;

FIG. 6 illustrates a distributed data communications system inaccordance with an embodiment of the present invention;

FIG. 7 illustrates a block diagram of a base station in accordance withan embodiment of the present invention;

FIG. 8 illustrates a block diagram of a server computer in accordancewith an embodiment of the present invention;

FIG. 9 illustrates a block diagram of a mobile station in accordancewith an embodiment of the present invention;

FIG. 10 illustrates a mobile station receiving interference from anadjacent sector in accordance with an embodiment of the presentinvention;

FIG. 11 illustrates coordinating scheduling of four-level quantizedbeams in accordance with an embodiment of the present invention;

FIG. 12 illustrates a table mapping a binary value to a quantized phasedifference in accordance with an embodiment of the present invention;

FIG. 13 illustrates a plot of the beamforming gain versus the phasedifference of two signals with 0 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention;

FIG. 14 illustrates a table showing the average gain of the combinedsignals in FIG. 13 relative to the signal transmitted from one of theantennas for each of the quantized phase zones in accordance with anembodiment of the present invention;

FIG. 15 illustrates a plot of the beamforming gain versus the phasedifference of two signals with 3 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention;

FIG. 16 illustrates a table showing the average gain of the combinedsignals in FIG. 15 relative to the signal transmitted from one of theantennas for each of the quantized phase zones in accordance with anembodiment of the present invention;

FIG. 17 illustrates a plot of the beamforming gain versus the phasedifference of two signals with 10 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention;

FIG. 18 illustrates a table showing the average gain of the combinedsignals in FIG. 17 relative to the signal transmitted from one of theantennas for each of the quantized phase zones in accordance with anembodiment of the present invention;

FIG. 19 illustrates a mobile station receiving an intended signal from afirst base station and receiving interference from adjacent sectors withvarying phase adjustments in accordance with an embodiment of thepresent invention;

FIG. 20 illustrates a phase adjustment map in accordance with anembodiment of the present invention;

FIG. 21 illustrates the frequency resources used at a base station inaccordance with an embodiment of the present invention;

FIG. 22 illustrates a CPE phase management table at base station A withvarious mobile station transmissions and interference data in accordancewith an embodiment of the present invention;

FIG. 23 illustrates a flow diagram depicting processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention;

FIG. 24 illustrates a flow diagram depicting processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention;

FIG. 25 illustrates an empty transmission schedule at a base station Ain accordance with an embodiment of the present invention;

FIG. 26 illustrates a transmission schedule after addressingfirst-priority interference from base station B in accordance with anembodiment of the present invention;

FIG. 27 illustrates a transmission schedule after addressingfirst-priority interference from base station C in accordance with anembodiment of the present invention;

FIG. 28 illustrates a transmission schedule after addressingfirst-priority interference from base station D in accordance with anembodiment of the present invention

FIG. 29 illustrates a transmission schedule after addressingsecond-priority interference from base station B in accordance with anembodiment of the present invention;

FIG. 30 illustrates a transmission schedule after addressingsecond-priority interference from base station D in accordance with anembodiment of the present invention;

FIG. 31 illustrates a transmission schedule after addressingthird-priority interference in accordance with an embodiment of thepresent invention;

FIG. 32 illustrates a transmission schedule after addressingfourth-priority interference in accordance with an embodiment of thepresent invention;

FIG. 33 illustrates a flow diagram depicting processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention;

FIG. 34 illustrates a flow diagram depicting processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention;

FIG. 35 illustrates a table mapping the three bit message to eightquantized phase angle zones/regions according to an embodiment of thepresent invention;

FIG. 36 illustrates a plot of the beamforming gain versus the phasedifference of two signals with 0 dB branch imbalance at a receivercorresponding to quantized phase difference zones according to anembodiment of the present invention;

FIG. 37 illustrates a table showing the average gain of the combinedsignal relative to the signal transmitted from one of the antennas foreach of the quantized phase zones according to an embodiment of thepresent invention;

FIG. 38 illustrates a table showing the best, second best and third bestphase adjustment steps for optimal signal combining for each of thephase difference measurement zones according to an embodiment of thepresent invention;

FIG. 39 illustrates a wireless system with a mobile station that is inthe coverage area of a base station and receiving interference from anadjacent base station;

FIG. 40 illustrates a wireless system similar to the wireless system inFIG. 39 with the addition of an additional mobile station MS2′; and

FIGS. 41-49 illustrate an example of how data transmissions amongmultiple base stations can be scheduled such that the interference toadjacent base station sectors is reduced, by coordinating the adjustmentof relative phases of the transmitted signals at each base stationaccording to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The present invention generally relates to systems and methods forcoordinating the scheduling of beamformed data to reduce interference.The levels of interference in a cellular wireless system are reduced bycoordinating the transmissions from each base station in the system sothat the level of interference at the subscriber devices is reduced. Acustomer premise equipment (CPE) uses a plurality of bits to quantizethe phase angle of the beamformed data received by CPE and reports it toits serving base station. The serving base station selects one of thephase adjustment angles based on the bits received from the CPE in orderto schedule the data transmission to the CPE. The phase adjustmentangles are in “n” degree steps. In an embodiment, two bits are used toquantize the phase angle reported by CPEs to their serving base stationsand four phase adjustments angles (i.e., in 90 degree steps) are used.The two bit allows the phase zones to be quantized into four differentlevels. Each phase angle adjustment is mapped to a single phase angledifference.

In another embodiment, three bits are used to quantize the phase anglereported by CPEs to their serving base stations and four phaseadjustments angles (i.e., in 90 degree steps) are used. The three bitallows the phase zones to be quantized into eight different levelsinstead of four. Each phase angle adjustment is mapped to two phaseangle differences. The additional quantization bit is used todifferentiate between the second most optimal phase angle correction andthe third most optimal phase angle correction.

FIG. 6 illustrates a networked computing system 600 including variouswireline and wireless computing devices that may be utilized toimplement any of the scheduling coordination processes associated withvarious embodiments of the present invention. The networked computingsystem 600 may include, but is not limited to, a group of remote basestation devices 606 a-c, any one of which may be associated with amacrocell, a microcell, or a picocell base station that may each be aneighboring base station to one or more short-range base station devices612 (e.g., a femtocell or a picocell device) within a particular regionof the networked computing system 600; a data communications network602, including both Wide Area Network (WAN) and Local Area Network (LAN)portions; a variety of wireless user equipment, including: cellularphone or PDA devices 608 a-c, 622, a laptop or netbook computer 624, anelectronic book device 626, along with any other common portablewireless computing devices well known in the art (e.g., handheld gamingunits, personal music players, video recorders, etc.) that are capableof communicating with the data communications network 602 utilizing oneor more of the remote base stations 606 a-c, the short-range basestation device 612, or any other common wireless or wireline networkcommunications technology; one or more network gateways or switchdevices 610 that can facilitate data communications processes within theLAN and between the LAN and the WAN of the data communications network602; a television device 616 (e.g., a high definition LCD or Plasmatelevision) that is optionally connected to a multi-media device 614(e.g., a set-top box, digital video recorder (DVR), or Blu-Ray™ playerdevice); and a desktop computer 620 optionally connected to an externalhard-drive device 618.

In an embodiment, the remote base station devices 606 a-c may representindividual base stations with a single antenna, individual base stationswith an antenna array configured for transmitting beamformedtransmissions, or a base station consisting of multiple sectors, eachwith a multi-antenna array. In addition, the remote base station devices606 a-c or the short-range base station device 612 may represent basestation 102 of FIG. 1.

In an embodiment, the remote base station devices 606 a-c, theshort-range base station device 612 (e.g., a femtocell or a picocelldevice), or any of the user equipment (608 a-c, 614, 616, 618, 620, 622,624, or 626), may be configured to run any well-known operating system,including, but not limited to: Microsoft® Windows®, Mac OS®, Google®Chrome®, Linux®, Unix®, or any well-known mobile operating system,including Symbian®, Palm®, Windows Mobile®, Google® Android®, MobileLinux®, MXI®, etc. In an embodiment, any of the remote base stations 606a-c may employ any number of common server, desktop, laptop, andpersonal computing devices.

In an embodiment, the user equipment (608 a-c, 622, 624, or 626) mayinclude any combination of common mobile computing devices (e.g., laptopcomputers, netbook computers, cellular phones, PDAs, handheld gamingunits, electronic book devices, personal music players, MiFi™ devices,video recorders, etc.), having wireless communications capabilitiesemploying any common wireless data commutations technology, including,but not limited to: GSM™, UMTS™, LTE™, LTE Advanced™, Wi-Max™, Wi-Fi™,etc. In addition, the user equipment (608 a-c, 614, 616, 618, 620, 622,624, or 626) may represent the receiver 108 of FIG. 1.

In an embodiment, either of the LAN or the WAN portions of the datacommunications network 602 of FIG. 6 may employ, but are not limited to,any of the following common communications technologies: optical fiber,coaxial cable, twisted pair cable, Ethernet cable, and powerline cable,along with any wireless communication technology known in the art. In anembodiment, any of the remote wireless base station 606 a-c, thewireless user equipment (608 a-c, 622, 624, or 626), as well as any ofthe other LAN connected computing devices (610, 614, 616, 618, or 620)may include any standard computing software and hardware necessary forprocessing, storing, and communicating data amongst each other withinthe networked computing system 600. The computing hardware realized byany of the network computing system 600 devices (606 a-c, 608 a-c, 610,612, 614, 616, 620, 622, 624, or 626) may include, but is not limitedto: one or more processors, volatile and non-volatile memories, userinterfaces, transcoders, and wireline and/or wireless communicationstransceivers, etc.

In addition, any of the networked computing system 600 devices (606 a-c,608 a-c, 610, 612, 614, 616, 620, 622, 624, or 626) may be configured toinclude one or more computer-readable media (e.g., any common volatileor non-volatile memory type) encoded with a set of computer readableinstructions, which when executed, performs a portion of any of theshort-range wireless communications optimization processes associatedwith various embodiments of the present invention.

FIG. 7 illustrates a block diagram of a base station device 700 (e.g., afemtocell, picocell, microcell or macrocell device) that may berepresentative of the base stations 606 a-c and 612 in FIG. 6. In anembodiment of the present invention, the base station device 700 mayinclude, but is not limited to, a baseband processing circuit includingat least one central processing unit (CPU) 702. In an embodiment, theCPU 702 may include an arithmetic logic unit (ALU, not shown) thatperforms arithmetic and logical operations and one or more control units(CUs, not shown) that extract instructions and stored content frommemory and then executes and/or processes them, calling on the ALU whennecessary during program execution. The CPU 702 is responsible forexecuting all computer programs stored on the base station device's 700volatile (RAM) and nonvolatile (ROM) system memories 704 and 726.

The base station device 700 may also include, but is not limited to, aradio frequency (RF) circuit for transmitting and receiving data to andfrom the network. The RF circuit may include, but is not limited to, atransmit path including a digital-to-analog converter 710 for convertingdigital signals from the system bus 720 into analog signals to betransmitted, an upconverter 708 for setting the frequency of the analogsignal, and a transmit amplifier 706 for amplifying analog signals to besent to the antenna 712 and transmitted as beamformed signals. Inaddition, the RF circuit may include, but is not limited to, a receivepath including the receive amplifier 714 for amplifying any individualor beamformed signals received by the antenna 712, a downconverter 716for reducing the frequency of the received signals, and ananalog-to-digital converter 718 for outputting the received signals ontothe system bus 720. The system bus 720 facilitates data communicationamongst all the hardware resources of the base station device 700. Theremay be any number of transmit/receive paths 730, 732, and 734 comprisingmultiple digital-to-analog converters, upconverters, and transmitamplifiers as well as multiple analog-to-digital converters,downconverters, and receive amplifiers in order to transmit and receiveas a beamforming base station. Additionally, antenna 712 may includemultiple physical antennas for transmitting beamformed communications.

The base station device 700 may also include, but is not limited to, auser interface 722; an operations and maintenance interface 724; memory726 storing application and protocol processing software; and a networkinterface circuit 728 facilitating communication across the LAN and/orWAN portions of the data communications network 602 (i.e., a backhaulnetwork).

In an embodiment of the present invention, the base station 700 may useany modulation/encoding scheme known in the art such as Binary PhaseShift Keying (BPSK, having 1 bit/symbol), Quadrature Phase Shift Keying(QPSK, having 2 bits/symbol), and Quadrature Amplitude Modulation (e.g.,16-QAM, 64-QAM, etc., having 4 bits/symbol, 6 bits/symbol, etc.).Additionally, the base station 700 may be configured to communicate withthe subscriber devices (e.g., 608 a-c, 622, 624, and 626) via anyCellular Data Communications Protocol, including any common GSM, UMTS,WiMAX or LTE protocol.

FIG. 8 illustrates a block diagram of a server computer 800 that may berepresentative of any of the remote service provider devices 606 a-c orthe base station 612 in FIG. 6, the base station 700 in FIG. 7, or anyother common network device known in the art such as a router, gateway,or switch device. The server computer 800 may include, but is notlimited to, one or more processor devices including a central processingunit (CPU) 804. In an embodiment, the CPU 804 may include an arithmeticlogic unit (ALU) (not shown) that performs arithmetic and logicaloperations and one or more control units (CUs) (not shown) that extractsinstructions and stored content from memory and then executes and/orprocesses them, calling on the ALU when necessary during programexecution. The CPU 804 is responsible for executing all computerprograms stored on the server computer's 800 volatile (RAM), nonvolatile(ROM), and long-term storage system memories, 802 and 810.

The server computer 800 may also include, but is not limited to, anoptional user interface 820 that allows a server administrator tointeract with the server computer's 800 software and hardware resourcesand to display the performance and operation of the networked computingsystem 600; a software/database repository 810 including: a phaseadjustment map 812 (e.g., statically or dynamically created phaseadjustment map 2000 in FIG. 20) that may include a listing of adjacentwireless base stations and their instantaneous transmission phaseadjustments; scheduling unit 814 for generating a CPE phase managementtable (e.g., CPE phase management table 2200 in FIG. 22 for multiplebase stations) for transmitting data to mobile stations associated withthe server computer or base station; a beamforming unit 816 forgenerating the beamformed signals for transmission to a particularmobile device; and a priority fixing unit 818 for determining a prioritylevel for interference associated with an adjacent interfering basestation. The base station 700 may include the components in thesoftware/database repository 810 for implementing the systems andmethods in accordance with the present invention.

In addition, the server computer 800 may include a modem 808 forformatting data communications prior to transfer; a transceiver 806 fortransmitting and receiving beamformed network communications amongstvarious network base stations, user equipment, and computing devicesutilizing the data communication network 602 of the networked computingsystem 600; and a system bus 822 that facilitates data communicationsamongst all the hardware resources of the server computer 800.

FIG. 9 illustrates a block diagram of a mobile station 900 that may berepresentative of any of the subscriber devices (e.g., 608 a-c, 622,624, and 626) shown in FIG. 6. The mobile station 900 may include, butis not limited to, components similar to those described above inrelation to the base station 700. Thus, mobile station 900 may include abaseband processing circuit 902 corresponding to the baseband processingcircuit in FIG. 7, a RF Circuit 904 corresponding to the RF circuit inFIG. 7, a memory 906 corresponding to the memory 726, a system bus 908corresponding to system bus 720, a user interface 910 corresponding touser interface 722, an operations and maintenance interface 912corresponding to the operations and maintenance interface 724, and aphase difference measurement unit 914.

In an embodiment, the phase difference measurement unit 914 measures thephase difference between incoming signals from each base station. Forexample, the phase difference measurement unit 914 will determine aphase difference measurement for the signals from the intended basestation, as well as determining a phase difference measurement forsignals received from adjacent base station sectors received asinterference. This measurement is needed at the mobile station 900because the phase difference between the signals will vary as thesignals may travel by different paths and arrive at the mobile station900 with a shifted phase difference. In addition, the phase differencemeasurement unit may measure and record the signal characteristics ofthe intended signals and interfering signals, including power levels,interference levels (e.g., a signal-to-interference-plus-noise (SINR)level or a carrier-to-interference-plus-noise (CINR) level), or othercharacteristics.

FIGS. 10-34 illustrate systems and methods for coordinating thescheduling of beamformed data to reduce interference using two bits toquantize the phase angle reported by CPEs to their serving base stationsaccording to an embodiment of the present invention. The serving basestation selects one of four phase adjustment angles (in 90 degree steps)based on the bits received from the CPE in order to schedule the datatransmission to the CPE. The two bit allows the phase zones to bequantized into four different levels. Each phase angle adjustment ismapped to a single phase angle difference in the present embodiment.

A quantized phase angle reporting and a quantized phase angle adjustmentare performed to reduce interference and to increase desired signalstrength at the CPE in accordance with an embodiment of the presentinvention. As described in more detail below, a mobile device/CPE (e.g.,108, 608 a-c, 622, 624, 626, 900, MS1 and MS2) measures the phasedifference (e.g., via phase difference measurement unit 914) between thetwo signals that it receives from each of the base station transmittersand transmits back the measurements to its serving base station. Thismeasurement is quantized to one of four values by rounding the measureddifference to the nearest 90 degrees. For example, if the measureddifference is 244°, then the nearest 90° step is 270°.

FIG. 10 illustrates a wireless system 1000 with a mobile station MS1receiving interference 1004 from an adjacent sector in accordance withan embodiment of the present invention. In the wireless system 1000, themobile station MS1 is in communication with base station BS1 viabeamformed transmission 1002. In an embodiment, mobile station MS1 maybe representative of mobile station 900, and base station BS1 and BS2may be representative of base station 700. While the base station BS1 isin communication with the mobile station MS1, the best signal from BS1is achieved when BS1 transmits to MS1 with a quantized phase adjustmentof 0° (i.e., the signals arriving at MS1 from each of the BS1 transmitsantennas combine to provide the strongest signal when no adjustment ismade to the relative phases of the signals emitted from BS1). An exampleof the constructive interference at the receiving mobile station is seenas the combined signals in plots 202 and 302.

As the mobile station MS1 receives the intended signal from base stationBS1, the mobile station MS1 also receives interference from the adjacentbase station BS2. In this case, the signal that MS1 receives from BS2can be attenuated the most when BS2 transmits with a quantized phaseadjustment of 270°. In other words, the best CINR or SINR at MS1 isachieved when BS1 is transmitting to MS1 with a phase adjustment of 0°and BS2 is transmitting to a different mobile station in its coveragearea with a phase adjustment of 270°.

FIG. 11 illustrates a wireless system 1100 similar to the wirelesssystem 1000 in FIG. 10 with the addition of an additional mobile stationMS2. In addition, FIG. 11 introduces the concept of coordinatingscheduling of four-level quantized beams. In this case, the phasedifference is quantized into four discrete regions, corresponding to aphase difference of 0°, 90°, 180°, and 270°. This quantization reducesthe amount of feedback required from a mobile station to a base stationwhen communicating phase difference information. The quantization alsoreduces computational overhead, while still providing exceptionalcontrol over the levels of constructive or deconstructive interference.This four-level quantization is explained further with reference toFIGS. 12-18.

Wireless system 1100 shows BS2 transmitting to a mobile station MS2 inits coverage area. The optimal combining of the signals arriving at MS2from BS2 occurs when BS2 adjusts the relative phases of itstransmissions by 180°. However, adequate performance at MS2 is stillachieved if BS2 uses a phase adjustment of 90° or 270°. In this case,BS2 transmits to MS2 with a phase adjustment of 270°, while at the sametime BS1 transmits to MS1 with a phase adjustment of 0°. The combinedsignal at MS2 is slightly degraded compared to the combining that couldbe achieved with a phase adjustment of 180°. However, the use of a phaseadjustment of 270° instead of 180° improves the CINR at MS1 by a fargreater amount than the loss in CINR at MS2. Thus, this optimizationconsiders the efficiency gained at each mobile station MS1 and MS2 whileconsidering the overall system efficiency for best efficiency gains.

Next, FIGS. 12-18 describe the four-level quantization of the phasedifference and the effect on signal strength at a receiver. In anexemplary system implementing this coordination scheme (e.g., wirelessbeamforming system 100 and networked computing system 600), the relativephases of the signals (e.g., 104 and 106) transmitted by a base station(e.g., 102, 606 a-c, 612, and 700) are adjusted in 90° steps. The mobiledevice/CPE (e.g., 108, 608 a-c, 622, 624, 626, 900, MS1 and MS2)measures the phase difference (e.g., via phase difference measurementunit 914) between the two signals that it receives from each of the basestation transmitters and transmits back the measurements to its servingbase station. This measurement is quantized to one of four values byrounding the measured difference to the nearest 90 degrees. For example,if the measured difference is 244°, then the nearest 90° step is 270°.

The quantization to two bits may be performed at the mobile device andthe quantized phase difference can be represented in a signaling messageas two binary bits. For example, the mapping between the two-bit messageand the phase difference can be applied as seen in FIG. 12.

Quantizing the phase difference to one of four values has the advantageof reducing the messaging overhead to a base station when compared toquantization to a larger number of values (e.g., it would require ninebinary bits to signal a phase difference quantized to 1 degree steps).This aspect helps promote the goals of efficiency while not beingcomputationally burdensome for scheduling.

When the base station (e.g., 102, 606 a-c, 612, and 700) or servercomputer 800 receives the quantized phase difference, it can adjust thephase on one of the transmitters (e.g., in one of the transmittingantennas in a beamforming antenna array) so that the phase difference ofthe beamformed signals arriving at the mobile station fall into one ofthe zones shown in FIG. 13.

FIG. 13 illustrates a plot 1300 of the beamforming gain versus the phasedifference of two signals with 0 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention. If the base station adjusts thephases so that the phase difference of the signals arriving at the userequipment falls into the 0° zone then the signals combine to provide thelargest increase in signal strength at the receiver. If the base stationadjusts the phases so that the phase difference of the signals arrivingat the user equipment falls into the 180° zone then the signals combineto provide the most reduction in signal strength at the receiver. If thesignals are aligned so that the phase difference falls into the 90° or270° zones then the combined signal may either have a gain or slightreduction in gain when compared to one of the originally transmittedsignals.

FIG. 14 illustrates a table 1400 showing the average gain of thecombined signals in FIG. 13 relative to the signal transmitted from oneof the antennas for each of the quantized phase zones in accordance withan embodiment of the present invention. On average, the strongest signalstrength is achieved if the phases are adjusted so that the phasedifference at the receiver falls into the 0° zone. If the phasedifference is adjusted so that it falls in either the 90° or 270° zonesthen on average the combined signal strength is 3 dB lower than theaverage signal strength achieved in the 0° zone. If the phase differenceis adjusted such that it falls in the 180° zone then on average thecombined signal is attenuated by 14 dB relative to the signal in the 0°zone.

FIG. 15 illustrates a plot 1500 of the beamforming gain versus the phasedifference of two signals with 3 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention. In this plot 1500, the beamforminggain is relative to the stronger of the two received signals.

FIG. 16 illustrates a table 1600 showing the average gain of thecombined signals in FIG. 15, relative to the stronger of the tworeceived signals, for each of the quantized phase zones in accordancewith an embodiment of the present invention. Phase differences in the0°, 90° and 270° zones show the best average signals strengths, whilephase differences falling in the 180° zone shows the best averagecombined signal attenuation.

FIG. 17 illustrates a plot 1700 of the beamforming gain versus the phasedifference of two signals with 10 dB branch imbalance at a receivercorresponding to quantized phase difference zones in accordance with anembodiment of the present invention. As in the case of FIG. 15, thebeamforming gain is relative to the stronger of the two receivedsignals. Note that in this case the gain in the 0° zone is less thanthat shown in FIG. 13 and FIG. 15. Additionally, the attenuation in the180° zone is less than that achieved when the relative signal strengthsis the signals from both of the transmit antennas are close together atthe receiver.

FIG. 18 illustrates a table 1800 showing the average gain of thecombined signals in FIG. 17, relative to the stronger of the tworeceived signals, for each of the quantized phase zones in accordancewith an embodiment of the present invention. As before, phasedifferences in the 0°, 90° and 270° zones show the best average signalsstrengths, while phase differences falling in the 180° zone shows thebest average attenuation for the combined signal.

Next, FIG. 19 illustrates a mobile station receiving an intended signalfrom a first base station and receiving interference from adjacentsectors with varying phase adjustments in accordance with an embodimentof the present invention. As will become apparent when viewing FIG. 19in conjunction with the phase adjustment map of FIG. 20, the basestation BS A in communication with the mobile station MS1 istransmitting a beamformed transmission signal 1902 with a phaseadjustment of 0 degree. At the same time and utilizing the same wirelessresources (e.g., frequency, channels, timeslots, etc.) adjacent basestation BS B is transmitting a beamformed signal 1904 with a phaseadjustment of 90 degrees. The beamformed transmission signal 1904 isreceived at MS 1 as interference rather than as a communication. Inaddition, base station BS C is transmitting a beamformed signal 1906with a phase adjustment of 180 degrees, and base station BS D istransmitting a beamformed signal 1908 with a phase adjustment of 270degrees. Signals 1906 and 1908 are also received as interference at MS1. Referring to FIGS. 19, 20, and 21, the transmission snapshot in FIG.19 corresponds to the phase adjustments used by base stations A, B, C,and D as scheduled in column 1, timeslot 1 of tables 2002, 2004, 2006,and 2008 in FIG. 20.

FIGS. 20-34 illustrate an example of how data transmissions amongmultiple base stations (e.g., base stations BS A, BS B, BS C, and BS Din FIG. 19) can be scheduled such that the interference to adjacent basestation sectors is reduced, by coordinating the adjustment of relativephases of the transmitted signals at each base station. The belowexample assumes two transmitters at each base station site (e.g.,similar to the two-transmitter beamforming antenna array 102 in FIG. 1)and assumes that the relative phases of the transmitted signals areadjusted in 90° steps (i.e., the phase differences are quantized in thefour-level quantization scheme shown in FIG. 12).

FIG. 20 illustrates a phase adjustment map in accordance with anembodiment of the present invention. In this example, there are fourbase stations in a cluster: base stations A, B, C, and D, similar to thetopology shown in FIG. 19, although it is apparent that the systems andmethods described herein may be applicable to any number of basestation, servers, or mobile devices.

In addition, in this example there are ten mobile stations incommunication with base station A, with CPE IDS 1-10 (e.g., see CPE IDS1-10 in FIG. 22). This example also assumes that each CPE/mobile stationcan measure the phase difference between the signals arriving from itsserving base station and the phase differences of the phases of signalsarriving from interfering base stations. The phase difference can bemeasured via pilot reference signals or other methods known in the art,or via a phase difference measurement unit similar to the phasedifference measurement unit 914 in FIG. 9. This example also assumesthat the mobile station/CPE reports this information back to the servingbase station and/or to a server computer for centralized scheduling.Note that in Time Division Duplexing (TDD) systems, it may possible forthe base station to exploit the reciprocity of the channel to determinethe phase difference between the signals arriving at a CPE being servedby the base station without explicit feedback from the CPE. However, theCPE will still need to measure the phase differences between the signalsarriving from the interfering base stations and their levels and reportthose phase differences and levels back to the serving base stationand/or server computer.

In regards to FIGS. 20 and 21, this example assumes further that anairlink framing structure has been defined, consisting of multipletimeslots, with each timeslot containing multiple frequency slots. ManyOFDM airlink structure are like this (e.g., LTE or AMC permutation modein WiMAX). In an embodiment, these systems and methods for coordinatingscheduling of beamformed data may be applied to any wireless technology,including, but not limited to: GSM™, UMTS™, LTE™, LTE Advanced™,Wi-Max™, Wi-Fi™, etc.

Consistent with an OFDM structure, in the present embodiment thewireless resources are structured such that there are thirty-twofrequency slots in a timeslot and that a data burst can be sent in eachtime/frequency slot (e.g., 32 data bursts can be sent in a singletimeslot—potentially one to each of up to 32 mobile stations/CPE). Aframing structure is also applied, where a frame consists of eighttimeslots.

Returning to FIG. 20, these tables illustrate a phase adjustment map2000 in accordance with an embodiment of the present invention. In thisexample, the four base stations A, B, C, and D are assigned a fixedphase transmission pattern in timeslots 0-3. The 32 frequency slots in atime slot are divided into eight groups of four each (i.e., there are 8frequency slots per group). Each group of frequency slots is allocated afixed phase adjustment value. This frequency structure is shown in FIG.21 as table 2100, illustrating the frequency resources used for a basestation. FIG. 21 shows the eight timeslots used to allocate resourcesfor the beamformed scheduling. In addition, the 32 frequency resourcesare divided equally into four groups, shown as columns 2102, 2104, 2106,and 2108. Thus, in FIG. 21 it is clear that Timeslot #1 corresponding tothe Phase Adjustment #2 refers to the group of frequencies (i.e.,channels) numbered 8-15. Applying this frequency table to the phaseadjustment map in FIG. 20, it can be seen that, for example, basestation B is transmitting at a phase adjustment of 180 degrees inTimeslot #1 for channels 8-15. At the same time, base station A istransmitting at a phase adjustment of 90 degrees for the identicaltimeslot/channel combination.

In FIG. 20, for timeslots 4-7, any phase may be transmitted in anyfrequency slot. These slots are used when the coordinating schedulingcannot be completed in the first four timeslots and for transmissionswhich are not interference limited. Thus, timeslots 4-7 may beconsidered to be “all purpose” timeslots for transmissions whereinterference is not an issue and for when guaranteed phase differencesare not required.

The assignment of phase adjustments to frequency and time slots in aphase adjustment map 2000 can be done in a variety of ways. For ease ofexplanation, the phase adjustment map is shown using a fixed assignmentin FIG. 20. In a fixed assignment, phase differences are allocatedbeforehand, using a reuse pattern, similar to the frequency reusepatterns commonly employed in cellular wireless systems. In a separateembodiment, the phase adjustment map may be dynamically determined basedon the phase difference measurements made by the mobile station. Thesemeasurements can be shared among the base stations, which can then agreeupon an appropriate phase adjustment map, or can be sent to a centralprocessing server that then determines an appropriate phase adjustmentmap for each base station and sends the maps to the base stations. In adynamic determination of the phase adjustment maps, the update rate ofthe phase adjustment maps may be as quick as every one to five airlinkframes, or may be relatively slow, on the order of one update everyseveral seconds. In another embodiment, the phase adjustment may bedetermined based on historical data or instantaneous factors such asdemand or interference levels.

Again note that it may not be necessary to attempt to reduceinterference at all mobile stations/CPE in the coverage area of a basestation. Many mobile stations/CPE will have good CINR to begin with, sothey will not need special handling. In this example, data to suchmobile stations/CPE can be transmitted in the “all purpose” timeslots4-7, or in timeslots 0-3 if the schedule can accommodate the additionalmobile stations.

FIG. 22 illustrates a CPE phase management table 2200 at base station Awith various mobile station transmission and interference data inaccordance with an embodiment of the present invention. For thisexample, Base Station A (BTS A) has 10 mobile stations/CPE to which itwill transmit data. The number of blocks of data and the optimal phaseadjustment angle to be used by BTS A to transmit to the CPEs is shown intable 2200. Additionally, the best phase adjustment angles that the basestations causing interference with each of the CPEs should use tominimize the interference levels is also shown in the table. Looking atthe data related to CPE #1 in table 2200, the CPE #1 receives thestrongest signal from base station A when base station A is transmittingat a 0 degree phase difference. In addition, CPE #1 receives the leastinterference from base station B when base station B is transmitting toits associated CPE on the same wireless resources at a phase adjustmentof 180 degrees.

The entries in the CPE phase management table 2200 in the interferingBTS phase adjustment cells have two numbers. The top number is the phaseadjustment in degrees from that base station that results in the lowestlevels of interference at the mobile station served by BTS A. The bottomnumber is a priority that is assigned to each of the interferers,indicating the relative priority of reducing the interference levels.Continuing with the reference to CPE #1, the phase adjustment thatresults in the lowest level of interference at the mobile station CPE #1from each of BTS B is 180 degrees, as mentioned above. In addition, forCPE #1 it is the priority 1 to reduce the interference from base stationB. In this scheduling algorithm, the priority ranking is 1 to 4, with 1being the highest priority. Note that as would be apparent to a personof ordinary skill in the art, the number of priority levels could begreater than or less than four. The priority can be assigned in avariety of ways, such as placing the highest priority on reducinginterference from the strongest interferers seen by CPEs with the lowestCINR, or on base stations causing the greatest levels of interference toa CPE, or using some other prioritization scheme. By way of example, inFIG. 19, reducing the interference from base station B may have been thehighest priority because the signal strength from base station B wouldbe the highest relative to the other adjacent interfering base stations(e.g., because of the relative distances from the base stations to themobile station MS 1).

Next, the coordinated scheduling algorithm will be described generallyby way of example in relation to flow diagrams in FIGS. 23 and 24,followed by a specific scheduling example in FIGS. 25-32.

FIG. 23 illustrates a flow diagram 2300 depicting processes forscheduling transmissions at a base station in accordance with anembodiment of the present invention. It should be understood that thisprocess could be executed using one or more computer-executable programsstored on one or more computer-readable media located on any one of thebase station devices (e.g., 606 a-c, 612, 700, and BS 1 and BS 2 ofFIGS. 10 and 11) or in the server computer 800 in FIG. 8. In blocks 2302and 2304, the process begins with scheduling the transmissions at basestation A in an empty schedule. Next, in block 2306, the processinitializes the priority level YY=1. Starting at the priority 1 levelmay reduce the worst interference before scheduling around lessimportant (i.e., lower priority) interfering transmissions. Next, atblock 2308, the process initializes the interfering bases station XX=B,where the interfering base station is selected from the group consistingof base stations B, C, and D. Again, note that process 2300 may beadaptable to any number of base stations, mobile devices, and prioritylevels. Next, at block 2310, the process addresses priority YY radiofrequency interference from interfering base station XX. In accordancewith the initialized values, the algorithm addresses the priority 1interference from base station B.

At block 2312, the process checks to see whether interference from eachbase station at that particular priority level has been addressed. Ifnot, the process moves to step 2314, where the algorithm addressesinterference from the next base station in the group (e.g., moves toaddressing interference for base station C after addressing interferencefrom base station B in step 2310, thereby updating the XX variable).When the interference from each base station has been addressed at theparticular priority level (e.g., YES in step 2312), the process moves tostep 2316 to check whether all priority levels have been addressed. IfNO, the process moves to step 2318 where the priority level isincremented (i.e., YY is incremented), and the process returns to block2310 to address interference for the adjacent base stations. Thus, theprocess 2300 cycles through the outer loop (addressing interference foreach priority level) and the inner loop at each priority level(addressing interference for each base station at a particular prioritylevel).

FIG. 24 illustrates a flow diagram 2400 depicting processes forscheduling transmissions at a base station in accordance with anembodiment of the present invention. This flow diagram may be used aloneor in conjunction with FIG. 23 to illustrate the scheduling process.Again, it should be understood that this process could be executed usingone or more computer-executable programs stored on one or morecomputer-readable media located on any one of the base station devices(e.g., 606 a-c, 612, 700, and BS 1 and BS 2 of FIGS. 10 and 11) or inthe server computer 800 in FIG. 8. The scheduling process 2400 begins atblock 2402 by determining the phase adjustments for best and next-bestsignal transmissions from base station A to each CPE served by basestation A. This information is portrayed as the column entitled “PhaseAdjustment for best signal level” in FIG. 22. Next, at block 2404, theprocess determines an optimal phase adjustment to reduce interferencelevels from each interfering base station to each of the CPEs served bybase station A. Next, at block 2406, the process determines a prioritylevel for interference reduction from each interfering base station foreach CPE served by base station A. This information determined in blocks2404 and 2406 is portrayed as the column entitled “Optimal PhaseAdjustment (in degrees) to reduce interference level and priority forinterference reduction” in FIG. 22.

In block 2408 the process starts at the highest priority level andchooses a CPE ID for which to schedule transmissions. For the CPE chosenin block 2408, the process determines the number of blocks to transmitat base station A to the CPE in block 2410. This information isportrayed as the column entitled “# Blocks to transmit” in FIG. 22.

Next, in block 2412, the process determines available wireless resourcesin the phase adjustment map for base station A, where base station A istransmitting at the phase adjustments for best and next-best signallevels for the chosen CPE. The available wireless resources meeting thisrequirement may be denoted as “Set 1.” By way of example, if the processwas performing the actions in step 2412 for CPE #1 in FIG. 22, theprocess would look for the timeslots in table 2002 that correspond tothe phase adjustment of 0 degree (for best signal levels) and for thetimeslots in table 2002 that correspond to the phase adjustments of 90degrees and 270 degrees (next-best signal levels). This Set 1 consistsof the first, second, and fourth columns in table 2002.

Next, at block 2414, the process determines a second set of wirelessresources corresponding to wireless resources in the phase adjustmentmap for the base station with highest priority level for interferencereduction where the interfering base station is transmitting at theoptimal phase adjustment angle for lowest interference signals level forthe chosen CPE. By way of example, the base station with the highestpriority level for interference reduction for CPE #1 is base station B,as seen in FIG. 22. FIG. 22 also states that the optimal phaseadjustment for the transmissions for base station B is 180 degrees.Looking at the phase adjustment map for base station B, i.e., table2004, the wireless resources that satisfy these requirements can befound: column 1, timeslot 2; column 2, timeslot 1; column 3, timeslot 0;and column 4, timeslot 3. As mentioned above, this is Set 2.

In block 2416, the process schedules transmissions at base station A forthe chosen CPE ID within the wireless resources overlapping in Set 1 andSet 2, starting with the overlapping wireless resources in Set 1 thatprovide the best signal level and proceeding with the overlappingwireless resources in Set 1 in order of the signal levels they provideto the CPE. In regards to Set 1 and Set 2 in the example above, the bestwireless resource for base station A would be column 1, timeslot 2, whenbase station A is transmitting with a phase adjustment of 0 degree. Thecorresponding wireless resource in base station B is column 1, timeslot2, when base station B is transmitting at a phase adjustment of 180degrees. Thus, by choosing this resource, the transmissions for CPE #1are scheduled to be transmitted at the most advantageous conditions formaximum signal reception from base station A, while being transmitted inthe same wireless resources where the interference from the base stationcausing the most interference is minimized. If there is not enough roomin column 1, timeslot 2, to contain all the transmissions to the chosenCPE ID then additional data to the CPE is scheduled in the wirelessresources with the next-best signal levels for the chosen CPE (e.g., theresources in column 2, timeslot 1, or column 4, timeslot 3 of phaseadjustment maps 2002 and 2004).

Next, at block 2418, the process continues to schedule the remainingdata blocks for transmission. If there are any blocks that could not bescheduled in the wireless resources in the previous step, block 2418either schedules the blocks in resources where the interfering phasesare not guaranteed, using the phase adjustment for best signaltransmissions from base station A, or block 2418 places those blocksinto a queue where they are retained for transmission in a futureairlink frame. By way of example, if there were remaining data to bescheduled for CPE #1 in the example above, the remaining blocks could bescheduled for transmission in timeslots 4-7 of base station A, orbuffered for transmission in a subsequent airlink frame. If transmittingin the resources where the interfering phases are not guaranteed, basestation A would transmit to CPE #1 with a phase shift of 0 degree, whichcorresponds to the “Phase Adjustment for Best Signal Level” of FIG. 22.

Finally, at block 2420 the scheduling process is repeated for remainingCPEs in communication with base station A at the same priority level,then at lesser priority levels until all data blocks are scheduled to betransmitted or until the schedule is full. Thus, the scheduling processschedules all priority-one interference for CPEs #2-10, and then repeatsthe process again at lesser priority levels until all the transmissionsare scheduled. Once a CPE has been scheduled at a particular prioritylevel, there is no need to schedule it again at lesser priority levels.Additionally, this process is scheduled at each base station (e.g., basestations B, C, and D) until all transmissions are scheduled.

By way of example, FIGS. 25-32 collectively schedule CPEs in the CPEphase management table shown in FIG. 22 for scheduling data fortransmission from base station A. Variants in the scheduling process caneasily be derived that are considered to be within the scope of thisinvention.

Thus, FIG. 25 illustrates an empty transmission schedule at a basestation A in accordance with an embodiment of the present invention.This is the start of the exemplary scheduling process, and may bereferred to as step one.

Next, FIG. 26 illustrates a transmission schedule after addressingfirst-priority interference from base station B in accordance with anembodiment of the present invention, and may be referred to as step two.In FIGS. 26-32, the CPE and number of blocks to be transmitted are shownin the time slot and frequency map. The number of blocks to betransmitted to a CPE is shown in brackets next to the CPE ID. The CPEsthat are scheduled in each step are shown in a bold font.

In the second step of addressing first-priority interference from basestation B, the optimal scheduling location for CPE #1 is timeslot #2 onthe frequency resources that have a phase adjustment of zero degree frombase station A. This optimal phase adjustment can be seen in FIG. 22,and the phase adjustment map for base station A is seen as table 2002.In timeslot #2, on those same frequency resources (i.e., resources wherebase station A is transmitting at a phase adjustment of zero degree),base station B is guaranteed to transmit to CPEs in its coverage areawith a phase adjustment of 180 degrees.

Note that only eight blocks of data can be transmitted in that timeslotwith that phase adjustment because there are only 8 channelstransmitting in this example at that phase adjustment during theparticular timeslot, as seen in FIG. 21. However, there are 14 blocks tobe transmitted to CPE #1. As a result, it is necessary to schedule theremaining six blocks of data to CPE #1 onto a different set oftime/frequency resources. Since the best gains are achieved by makingsure that the transmissions to CPE #1 are scheduled for when basestation B uses a phase adjustment of 180 degrees, the schedulingalgorithm should choose time/frequency resources where base station Btransmits with a 180 degree phase adjustment. The algorithm should alsochoose a phase adjustment from base station A that is within +/−90degrees of the optimal phase adjustment from base station A. Thissecond-best phase adjustment may correspond to the phase adjustment fornext-best signal levels as mentioned in block 2412 of FIG. 24. In thiscase, that means a phase adjustment of 90 degrees or 270 degrees (i.e.,a +270 degree phase adjustment is equivalent to a −90 degree phaseadjustment). In this case, the remaining six blocks are scheduled fortimeslot 1, on the frequency resources where base station A has a phaseadjustment of 90 degrees and base station B has a phase adjustment of180 degrees. The result of this scheduling can be seen in FIG. 26, whereeight blocks of data to be transmitted to CPE #1 are scheduled in thefirst column in timeslot 2, and the remaining six blocks of data arescheduled in the second column, timeslot 1.

Similarly, the optimal scheduling location for CPE #5 is in timeslot #1on the frequency resources with a phase adjustment of 180 degrees frombase station A (e.g., see FIG. 21, column entitled “Phase Adjustment forbest signal level”). Cross-referencing the phase adjustment maps in FIG.20, it is determined that base station B transmits with a phaseadjustment of 270 degrees on this set of time/frequency resources. Sincethere are only 6 blocks to be transmitted to CPE #5, all of the blockscan be scheduled on these time/frequency resources. Again, the result ofscheduling CPE #5 is seen in FIG. 26, where six blocks of data to betransmitted to CPE #1 are scheduled in the third column in timeslot 1.

Next, the remaining CPE with first-priority interference from basestation B, i.e., CPE #10, is scheduled by the scheduling algorithm. CPE#10 transmissions are scheduled for timeslot 0 in the frequencyresources with a phase adjustment of 270 degrees from base station A.Base station B will transmit with a phase adjustment of 270 degrees onthese resources, minimizing the level of interference seen at this CPE.Since CPE #10 has ten blocks to transmit, eight of the blocks arescheduled for these time/frequency resources, and in this example theremaining blocks are scheduled for timeslot 3 on the frequency resourceswith a phase adjustment of 0 degree from base station A and 270 degreesfrom base station B. The updated schedule is shown in FIG. 26.

Next, the scheduling algorithm addresses priority 1 interference frombase station C. The results of this scheduling step are seen in FIG. 27,and may be referred to as step three. In addressing the priority 1interference from base station C, the transmissions for CPE #3 and CPE#8 are scheduled in a similar manner to the transmissions in step two.Eight of the twelve data blocks to be transmitted to CPE #3 arescheduled for timeslot 2, phase adjustment of 90 degrees, whichcorresponds to a phase adjustment of 0 degree at base station C (e.g.,see phase adjustment maps 2002 and 2006). The remaining four data blocksfor CPE #3 are scheduled on timeslot 0, again with a phase adjustment of0 degree at base station C, but a next-best phase adjustment of 0 degreeat base station A.

The two blocks of data for CPE #8 are scheduled for their optimaltime/frequency resources on timeslot 3, with a phase adjustment of 270degrees from base station A and zero degree from base station C. Theupdated schedule is shown in FIG. 27.

Next, the scheduling algorithm addresses priority 1 interference frombase station D. FIG. 28 illustrates a transmission schedule afteraddressing priority 1 interference from base station D in accordancewith an embodiment of the present invention, and this step may bereferred to as step four. Looking at the table 2200 in FIG. 22, it canbe seen that only CPE #2 is receiving priority 1 interference from basestation D. All eight blocks for CPE #2 are scheduled for timeslot 1 witha phase adjustment of 0 degree from base station A and 270 degrees forbase station D.

After having addressed the priority 1 interference for base station B,C, and D, the scheduling algorithm next schedules the priority 2 CPEs onbase station B. This scheduling is seen in FIG. 29, which illustrates atransmission schedule after addressing second-priority interference frombase station B in accordance with an embodiment of the presentinvention. This step may be referred to as the fifth step. Eight blocksfor CPE #7 are scheduled in the optimal position in timeslot #1 whilethe remaining two blocks are scheduled for timeslot 2 where the phaseadjustment for base station B is still the optimal 0 degree and thephase adjustment from base station A is suboptimal, but still within+/−90 degrees of optimum, representing the next-best phase adjustmentfrom the serving base station. The updated schedule is shown in FIG. 29.

In the sixth step, the scheduling algorithm would schedule the priority2 CPEs on base station C. However, there are no CPEs to be scheduled, sothe algorithm moves to the next step (e.g., see FIG. 22).

In the seventh step, the algorithm addresses the priority 2 CPEs inrelation to base station D. FIG. 30 illustrates the transmissionschedule after addressing priority 2 interference from base station D inaccordance with an embodiment of the present invention. The optimalscheduling location for CPE #4 is on timeslot 1 on the frequencyresources with a phase adjustment of 90 degrees from base station A anda phase adjustment of 0 degree from base station D. Since there arealready six blocks of data scheduled on those resources and there areonly eight such resources available, only two of the blocks of data forCPE #4 can be sent on those resources. The remaining four blocks aresent on timeslot 3 with a phase adjustment from base station A of 180degrees (i.e. using the next-best phase adjustment) and a phaseadjustment of 0 degree from base station D.

For step eight, there is only one priority 3 CPE to schedule. FIG. 31illustrates the transmission schedule after addressing priority 3interference in accordance with an embodiment of the present invention.In this example, the optimal location for transmissions to CPE #6 has aphase adjustment of 180 degrees from base station A, which correspondsto wireless resources in the third column of phase adjustment map 2002.In regards to the interference received by CPE #6, there are twopriority 3 interference sources, the first being from base station B,while the second is from base station D (e.g., see FIG. 22). Looking atFIG. 22 it can be seen that the optimal phase adjustment to reduceinterference from base station B and D is 0 degree. Cross-referencingthe phase adjustment map 2002 with the phase adjustment maps 2004 and2008 (corresponding to base stations B and D), it can be determinedthere are two optimum slots in the transmission schedule. In this case,the algorithm can schedule the blocks for CPE #6 in timeslot 2, column3, where the interference from base station B will be reduced, or ontimeslot 3, column 3, where the interference from base station D will bereduced. In this case, it is assumed that the algorithm selects toschedule four resource blocks to be sent on timeslot 3 and two resourceblocks sent on timeslot 2. The updated schedule after the eighth step isshown in FIG. 31

In the ninth step, there is one priority 4 CPE to schedule, i.e., CPE #9(e.g., see FIG. 22). This CPE has the lowest priority level forscheduling. Since the best signal for this CPE is with a phaseadjustment of 270 degrees from base station A, the algorithm schedulestransmissions to this CPE in the available time/frequency resources withthis phase adjustment. Thus, FIG. 32 illustrates a transmission scheduleafter addressing priority 4 interference in accordance with anembodiment of the present invention.

In the scheduling example above, the example shows how all the CPEs arescheduled. In some cases it may not be possible to match up all CPEtransmissions with either a fully optimal set of phase adjustment fromthe serving and interfering base stations, or a next-best, sub-optimalset of phase adjustments (i.e., optimal for the interfering base stationand +/−90 degrees from optimal for the serving base station). In thosecases the CPE transmissions can be scheduled on timeslots 4-7, where noguarantees are made on the phase adjustments from any base stations.However, the serving base station may still use beamforming transmissionto optimize the downlink to the mobile devices while transmitting intimeslots 4-7. Alternatively, the blocks to be transmitted to a CPE maybe buffered for scheduling in a subsequent airlink frame.

Although in the above example the scheduling of transmissions to mobiledevices/CPE served by base stations B, C, and D is not shown, thesetransmissions are scheduled in a similar manner to those at base stationA. As long as base stations B, C, and D adjust their phases according tothe phase adjustment maps previously agreed to, the scheduling ofparticular CPEs in certain time/frequency slots can be performedindependently at each of these base stations.

FIGS. 33 and 34 illustrate another embodiment of the scheduling process.FIG. 33 illustrates a flow diagram 3300 of processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention. This flow diagram may be used alone or in conjunctionwith the scheduling processes shown in FIGS. 23 and 24 to illustrate thescheduling process. Again, it should be understood that this processcould be executed using one or more computer-executable programs storedon one or more computer-readable media located on any one of the basestation devices (e.g., 606 a-c, 612, 700, and BS 1 and BS 2 of FIGS. 10and 11) or in the server computer 800 in FIG. 8, or in the wireless userequipment 608 a-c, 622, 624, 626. The scheduling process 3300 begins atblock 3302 by measuring a first phase difference of a first beamformedsignal from a first base station at a first mobile station. In oneexample, the measurement may be performed by a phase differencemeasurement unit 914. At block 3304 the process measures a second phasedifference of a second beamformed signal from a second base station atthe first mobile station.

Next, at block 3306, the process determines a first phase adjustment tothe first beamformed signal based on the first phase differencemeasurement. This phase adjustment may be a four-level quantized phaseadjustment, and may be determined at the CPE, at a base station, or at acentral server computer. This first phase adjustment may correspond tothe “Phase Adjustment for best signal level” in FIG. 22. At block 3308,the process schedules a first data package in a first wireless resourcewith the first phase adjustment at a first base station in coordinationwith an associated second phase adjustment of a second wireless resourceat a second base station. This scheduling process may be performedaccording to the scheduling algorithm described in FIGS. 20-32. Finally,at block 3310, the process transmits the first data package as a firstbeamformed signal to the first mobile station.

FIG. 34 illustrates another flow diagram of processes for schedulingtransmissions at a base station in accordance with an embodiment of thepresent invention. This flow diagram may be used alone or in conjunctionwith the scheduling processes shown in FIGS. 23, 24, and 33 toillustrate the scheduling process. Again, it should be understood thatthis process could be executed using one or more computer-executableprograms stored on one or more computer-readable media located on anyone of the base station devices (e.g., 606 a-c, 612, 700, and BS 1 andBS 2 of FIGS. 10 and 11) or in the server computer 800 in FIG. 8, or, orin the wireless user equipment 608 a-c, 622, 624, 626.

Referring to FIG. 34, the scheduling process 3400 begins at block 3402by measuring a first phase difference of a first beamformed signal froma first base station at a mobile station. Next, at block 3404, theprocess measures a second phase difference of a second beamformed signalfrom a second base station at the mobile station. Next, at block 3406the process determines a first phase adjustment to the first beamformedsignal based on the first phase difference measurement to increase thegain of the first beamformed signal at the mobile station. This firstphase adjustment may correspond to the “Phase Adjustment for best signallevel” in FIG. 22. At block 3408 the process determines an optimal phaseadjustment to the second beamformed signal to reduce the gain of thesecond beamformed signal when received by the mobile station. Thissecond phase adjustment may correspond to the “Optimum Phase Adjustment(in degrees) to reduce interference level and priority for interferencereduction” in FIG. 22. Next, at block 3410, the process continues bylocating a wireless resource in a phase adjustment map at the first basestation that corresponds to the first phase adjustment for the firstbeamformed signal and the second phase adjustment for the secondbeamformed signal. Finally, at block 3412 the first data package istransmitted as a first beamformed signal in the located wireless signalto the first mobile station. Thus, by increasing the gain of theintended signal and decreasing the gain of the second signal, the SINRof the signal to an intended mobile station is greatly improved,improving signal quality for an end user.

FIGS. 35-49 illustrate systems and methods for coordinating thescheduling of beamformed data to reduce interference using more than twobits (e.g., three bits) to quantize the phase angle reported by CPEs totheir serving base stations according to another embodiment of thepresent invention. A customer premise equipment (CPE) uses three bits toquantize the phase angle of the beamformed data received by CPE andreports it to its serving base station. The serving base station selectsone of the phase adjustment angles based on the bits received from theCPE in order to coordinate scheduling of the data transmission to theCPE. The phase adjustment angles are in “m” degree steps (e.g., in 90degree steps). The three bit allows the phase zones to be quantized intoeight different regions compared to four when two bits are used. Thethird bit is used to differentiate between the second most optimal phaseangle adjustment and the third most optimal phase angle adjustment. Inthe present embodiment, the phase adjustment angles are in 90 degreesteps so each phase angle adjustment is mapped to two phase angleregions.

A quantized phase angle reporting and a quantized phase angle adjustmentare performed to reduce interference and to increase desired signalstrength at the CPE in accordance with an embodiment of the presentinvention. As described in more detail below, a mobile device/CPE (e.g.,108, 608 a-c, 622, 624, 626, 900, MS1 and MS2) measures the phasedifference (e.g., via phase difference measurement unit 914) between thetwo signals that it receives from each of the base station transmittersand transmits back the measurements (also may be referred to as “thephase difference/angle information” or “quantized phase difference/angleinformation”) to its serving base station. This measurement is quantizedto one of eight values by rounding the measured difference to thenearest of the angles in the form 22.5°+n*45°, where 0<=n<=7.

FIG. 35 illustrates a table 3500 mapping the three bit message (orquantized phase angle information) to eight quantized phase anglezones/regions according to an embodiment of the present invention. Eachof the three bit binary values is mapped to a quantized phasedifference, a range of phase differences, and a zone name. For example,the binary value “000” is associated with the quantized phase differenceof 337.5°, the range of phase differences of 315° to 360°, the zone nameof 0° Zone Low Side. The binary value “001” is associated with thequantized phase difference of 22.5°, the range of phase differences of0° to 45°, and the zone name of 0° Zone High Side.

FIG. 36 illustrates a plot 3600 of the beamforming gain versus the phasedifference of two signals with 0 dB branch imbalance at a receivercorresponding to quantized phase difference zones according to anembodiment of the present invention. The eight zones in FIG. 36correspond to the eight zones listed in table 3500.

Referring to FIGS. 35 and 36, a quantized phase angle reporting and aquantized phase angle adjustment are performed to reduce interferenceand to increase desired signal strength at the CPE according anembodiment of the present invention. A mobile device/CPE 608 a-c, forexample, measures the phase difference between the two signals that itreceives from each of the base station transmitters and transmits backthe measurements to its serving base station. This measurement isquantized by the mobile device to one of eight values in table 3500 byrounding the measured difference to the nearest of the angles in theform 22.5°+n*45°, where 0<=n<=7. The quantized phase differenceinformation is transmitted to the serving base station in a signalingmessage as three binary bits.

Quantizing the phase difference to one of eight values has the advantagethat the messaging overhead to a base station is reduced when comparedto quantization to a larger number of values (e.g., it would requirenine binary bits to signal a phase difference quantized to 1 degreesteps). This helps efficiency while not being computationally burdensomefor scheduling.

When the serving base station (or server computer 800) receives thequantized phase difference, it can adjust the phase on one of thetransmitters (e.g., in one of the transmitting antennas in a beamformingantenna array) so that the phase difference of the beamformed signalsarriving at the mobile station fall into one of the eight zones. In thepresent embodiment, only four phase adjustment angles are used: 0degree, 90 degrees, 180 degrees and 270 degrees (=−90 degrees). Morethan four phase adjustment angles may be used in other embodiments.

The optimum phase adjustment is zero degree if the measured phasedifference falls into one of the zero degree zones. The optimum phaseadjustment is 90 degrees if the phase measurement falls into one of the90 degree zones. This will cause the signals arriving at the CPE to havea phase difference of between 315 degrees (i.e., −45 degrees) and 45degrees, which provides the most gain. Similarly, the optimal phaseadjustment for signals with phase measurements that fall into the 180degree and 270 degree zones are 180 degrees and 270 degrees,respectively. The second most optimal phase adjustment/correctiondepends on where in a given zone a phase measurement falls.

FIG. 37 illustrates a table 3700 showing the average gain of thecombined signal relative to the signal transmitted from one of theantennas for each of the quantized phase zones according to anembodiment of the present invention. Table 3700 has a first column 3702listing the phase zones, a second column 3704 listing an average gain inthe signal received by the mobile device for a particular phase zone,and a third column 3706 listing the difference from 0 degree phase zoneaverage gain.

On average, the strongest signal strength is achieved if the phases areadjusted so that the phase difference at the receiver falls into one ofthe 0° zones, i.e., 0° Zone Low Side or 0° Zone High Side. If the phasedifference is adjusted so that it falls in either the 90° or 270° zones,then on average the combined signal strength is 3 dB lower than theaverage signal strength achieved in the 0° zone. If the phase differenceis adjusted such that it falls in the 180° zone, then on average thecombined signal is attenuated by 14 dB relative to the signal in the 0°zone. However, if the phase can be adjusted so that it falls into eitherthe 90° Low Side or 270° High Side, then the combined signal strength ison average only 1.4 dB lower than the optimum adjustment where thephases difference would fall in the 0° Zone Low Side (or 0° Zone HighSide). Since the phase adjustment takes place in 90 degree steps in thepresent embodiment, the second best phase adjustment depends on whetherthe phase difference detected by the mobile device falls onto the LowSide or High Side of the phase measurement zones.

FIG. 38 illustrates a table 3800 showing the best, second best and thirdbest phase adjustment steps for optimal signal combining for each of thephase difference measurement zones according to an embodiment of thepresent invention. The phase adjustment is performed in 90 degrees stepsin the present embodiments. The phase adjustments are made bysubtracting the phase measurements to arrive at the adjusted phasedifference. For example, a phase adjustment of 90 degrees means that 90degrees should be subtracted from the phase difference measurement toarrive at the final phase after adjustment.

The best phase adjustment places the adjusted signal in the 0° Zone LowSide or 0° Zone High Side. The 2nd best phase adjustment places theadjusted signal in the 90° Zone Low Side or 270° Zone High Side. The 3rdbest phase adjustment places the adjusted signal in the 90° Zone HighSide or 270° Zone Low Side. For example, if the mobile device measuresthe signal phase difference and transmits to the serving base stationthat the signals are being received at 0° Zone Low Side, the best phaseadjustment is 0° to place the signals being received in 0° Zone LowSide. The second best phase adjustment is 270° to place the signalsbeing received in 90° Zone Low Side. Third best adjustment is 90° toplace the signals being received in 270° Zone Low Side. The average gaindifference between the second best adjustment and the third bestadjustment is 3.5 dB, as noted by table 3700. The use of three bits toquantize the phase zones into eight zones by the mobile device enablethe serving base station to identify the second and the third best phaseadjustments.

For interfering signals, the largest reduction in interfering signalstrength is obtained when the phases of the interfering signals areadjusted such that they fall in the 180° Zone Low Side or 180° Zone HighSide. The second best case for interference reduction is when theinterfering signals are phase adjusted such that they fall into the 90°Zone High Side or 270° Zone Low Side. Unless the phases of theinterfering signals can be adjusted to fall within one of the 180°Zones, the interfering signal cannot be reduced significantly and may infact experience some gain. The average interference level jumps from anaverage −8.2 dB when the phase adjustment results in a signal that fallsin the best interference reduction zone (i.e., within the 180° Zones) toan average of 0.9 dB when the phase adjustment results in a signal thatfalls in the second best interference reduction zone (i.e., within the90° Zone High Side or 270° Zone Low Side). Accordingly, it is desirableto schedule data transmissions from a base station to a mobile stationin such a way that they occur when the phase adjustments from aninterfering base station result in the interfering signal phase fallingin the 180° Zones at the mobile station.

FIG. 39 illustrates a wireless system 3900 with a mobile station MS1′that is in the coverage area of a base station BS1′ and receivinginterference 3504 from an adjacent base station BS2′. Mobile stationMS1′ is in communication with base station BS1′ via beamformedtransmission 3902. In an embodiment, mobile station MS1′ may berepresentative of mobile station 900, and base station BS1′ and BS2′ maybe representative of base station 700. The difference in phases of thereference signals that MS1′ receives from BS1′ is quantized into eightdiscrete regions, corresponding to a phase difference of 337.5° (or 0°Zone Low Side), 22.5° (or 0° Zone High Side), 67.5° (or 90° Zone LowSide), 112.5° (or 90° Zone High Side), 157.5° (or 180° Zone Low Side),202.5° (or 180° Zone Low Side), 247.5° (or 270° Zone High Side), and292.5° (or 270° Zone Low Side). This quantization reduces the amount offeedback required from a mobile station to a base station whencommunicating the phase difference information. The quantization alsoreduces computational overhead, while still providing exceptionalcontrol over the levels of constructive or deconstructive interference.

In wireless system 3900, the difference in phases of the referencesignals that MS1′ receives from BS1′ falls in the 180° Zone High Side(i.e., the phase difference is in the range 180° to 225°). The bestsignal from BS1′ is achieved when BS1′ transmits to MS1′ with a phaseadjustment of 180° to the signals transmitted to MS1′. The signals thatMS1′ receives from BS2′ is attenuated the largest amount when BS2′adjusts the relative phases of its transmissions by 270°. In otherwords, the best CINR at MS1′ is achieved when BS1′ is transmitting toMS1′ with a phase adjustment of 180° and BS2′ is transmitting to adifferent CPE in its coverage area with a phase adjustment of 270°.

FIG. 40 illustrates a wireless system 4000 similar to the wirelesssystem 3900 in FIG. 39 with the addition of an additional mobile stationMS2′. Wireless system 4000 shows BS2′ transmitting to a mobile stationMS2′ in its coverage area with a phase adjustment of 270°. The best CINRat MS1′ is achieved when BS1′ transmits to MS1′ with a phase adjustmentof 180° since the phase difference falls in the 180° Zone High Side. Seetable 3800. The second best CINR is achieved if BS1′ transmits with aphase adjustment of 270°. The third best CINR is achieved if BS1′transmits with a phase adjustment of 90°. In an embodiment, BS1′coordinates its data transmission to MS1′ by selecting the time slotsassociated with the phase adjustment of 180°, the phase adjustment of270°, and the phase adjustment of 90°.

FIGS. 41-49 illustrate an example of how data transmissions amongmultiple base stations can be scheduled such that the interference toadjacent base station sectors is reduced, by coordinating the adjustmentof relative phases of the transmitted signals at each base stationaccording to an embodiment of the present invention. The systems andmethods disclosed herein for coordinating scheduling of beamformed datamay be applied to any wireless technology, including, but not limitedto: GSM™, UMTS™, LTE™, LTE Advanced™, Wi-Max™, Wi-Fi™, etc.

The present example assumes that an airlink framing structure has beendefined, consisting of eight timeslots, with each timeslot containingmultiple frequency slots, as with the previous example that used atwo-bit quantization. See FIG. 20 and the phase adjustment map 2000. Thefour base stations A, B, C, and D are assigned a fixed phasetransmission pattern in timeslots 0-3. The 32 frequency slots in a timeslot are divided into eight groups of four each. Each group of frequencyslots is allocated a fixed phase adjustment value. For timeslots 4-7,any phase may be transmitted in any frequency slot. These slots are usedwhen the coordinating scheduling cannot be completed in the first fourtimeslots and for transmissions which are not interference limited.Thus, timeslots 4-7 may be considered to be “all purpose” timeslots fortransmissions where interference is not an issue and for when guaranteedphase differences are not required.

The assignment of phase adjustments to frequency and time slots in aphase adjustment map can be done in a variety of ways, e.g., a fixedassignment or dynamic determination, as explained in a previous example.In a fixed assignment, phase differences are allocated beforehand, usinga reuse pattern, similar to the frequency reuse patterns commonlyemployed in cellular wireless systems. In a dynamic assignment, thephase adjustment map is dynamically determined based on the phasedifference measurements made by the mobile station.

FIG. 41 illustrates a CPE phase management table 4100 at base station Awith various mobile station transmission and interference data inaccordance with an embodiment of the present invention. For thisexample, Base Station A (BTS A) has 10 mobile stations/CPE to which itwill transmit data. The number of blocks of data and the zones intowhich the measured base station reference signals fall are shown intable 4100. The optimal phase adjustment angle to be used by BTS A totransmit to the CPEs along with the second and third best phaseadjustments are also is shown table 4100. Additionally, the best phaseadjustment angles that the base stations causing interference with CPEsshould use to minimize the interference levels is shown in the table.

The entries in the interfering BTS phase adjustment cells have twonumbers. The top entry is the phase adjustment in degrees for a giveninterfering BTS that results in the lowest levels of interference at themobile station when signals are received from that interfering BTS. Thebottom entry is a priority that is assigned to each of the interferers,indicating the relative importance of reducing the interference levels.In the present embodiment, the priority ranking is 1 to 4, with 1 beingthe highest priority and having the greatest need to reduceinterference. The priority can be assigned in a variety of waysaccording to implementation. For example, the priority can be assignedto place the highest priority on reducing interference from thestrongest interferers seen by CPEs with the lowest CINR, or on basestations causing the greatest levels of interference to a CPE, or usingsome other prioritization scheme.

FIGS. 42-47 illustrate a process for coordinating the scheduling ofbeamformed data to reduce interference according to an embodiment of thepresent invention. FIG. 42 illustrates an empty transmission schedule4200 at a base station A at the start of the scheduling process.

FIG. 43 illustrates a transmission schedule 4300 for addressingfirst-priority interference (or priority 1 interference) from basestation B according to an embodiment of the present invention. The CPEand number of blocks to be transmitted are shown in the time slot andfrequency map. The number of blocks to be transmitted to a CPE is shownin square parentheses next to the CPE ID. The CPEs that are scheduled ineach step are shown in a bold font.

In the step associated with schedule 4300, the optimal schedulinglocation for CPE #1 is timeslot #2 on the frequency resources that havea phase adjustment of zero degree from base station A. In timeslot #2,on those same frequency resources, base station B is guaranteed totransmit to CPEs in its coverage area with a phase adjustment of 180degrees.

There are 14 blocks of data to be transmitted to CPE #1. Only eight ofthe 14 blocks of data are transmitted in timeslot #2 with the phaseadjustment of zero degree because there are only 8 time/frequencyresources available in this example. The remaining six blocks of dataneeds to be transmitted to CPE #1 using a different set oftime/frequency resources. Since the best gains are achieved by makingsure that the transmissions to CPE #1 are scheduled for when basestation B uses a phase adjustment of 180 degrees, the scheduling processshould choose the time/frequency resources where base station Btransmits with a 180 degree phase adjustment. The scheduling processalso should choose the second best phase adjustment from base station A.In this case that means a phase adjustment of 90 degrees (see table4100). The remaining six blocks are scheduled for timeslot #1, on thefrequency resources where base station A has a phase adjustment of 90degrees and base station B has a phase adjustment of 180 degrees.

Similarly, the optimal scheduling location for CPE #5 is in timeslot #1on the frequency resources with a phase adjustment of 180 degrees frombase station A. Base station B transmits with a phase adjustment of 270degrees on this set of time frequency resources. Since there are only 6blocks to be transmitted to CPE #5, all of the blocks can be scheduledon these time/frequency resources.

There are 22 blocks of data to be transmitted to CPE #10 from basestation A. Ideally all of these blocks should be scheduled fortransmission in timeslot #0 in the frequency resources with a phaseadjustment of 270 degrees. Base station B will transmit with a phaseadjustment of 270 degrees on these resources, minimizing the level ofinterference seen at this CPE #10. Only eight of the twenty-two blockscan be scheduled for these time/frequency resources. Eight additionalblocks can be scheduled in the second best option for CPE #10, which isin timeslot #3 on the frequency resources with a phase adjustment of 0degree from base station A (see table 4100).

The third best option for transmissions to CPE #10 is where the phaseadjustment from base station A is 180 degrees and from base station B is270 degrees. This is located in timeslot #1. However, six of the eightfrequency resources with these phase adjustments are already in use forCPE #5 transmissions, so only two of the remaining six blocks of datafor CPE #10 can be scheduled on these resources. The remaining fourblocks of data for CPE #10 are scheduled in timeslot #4. In this case,the transmit phase adjustment for the transmissions is set to theoptimal of 270 degrees from base station A. Note that there are noguarantees on the phase adjustments that will be used by base station Bon these resources.

FIG. 44 illustrates a transmission schedule 4400 for addressingfirst-priority interference from base station C according to anembodiment of the present invention. In addressing the first-priorityinterference from base station C, the transmissions for CPE #3 and CPE#8 are scheduled in a similar manner to the transmissions for CPE #10.Eight of the twelve data blocks to be transmitted to CPE #3 arescheduled for timeslot 2, phase adjustment of 90 degrees, whichcorresponds to a phase adjustment of 0 degrees at base station C. Theremaining four data blocks for CPE #3 are scheduled on timeslot #0,again with an optimal phase adjustment of 0 degree at base station C forinterference minimization, but a second best phase adjustment of 0degree for desired signal combining at base station A.

The two blocks of data for CPE #8 are scheduled for their optimaltime/frequency resources on timeslot #3, with a phase adjustment of 270degrees from base station A and zero degree from base station C.

FIG. 45 illustrates a transmission schedule 4500 after addressingfirst-priority interference from base station D according to anembodiment of the present invention. All eight blocks for CPE #2 arescheduled for timeslot #1 with a phase adjustment of 0 degree from basestation A and 270 degrees for base station D.

FIG. 46 illustrates a transmission schedule 4600 for addressingsecond-priority interference (or priority 2 interference) from basestation B according to an embodiment of the present invention. Thepriority 2 interferences are processed after the priority 1 interferencefor base stations B, C, and D have been processed. Eight blocks for CPE#7 are scheduled in the optimal position in timeslot #1 while theremaining two blocks are scheduled for timeslot #2 where the phaseadjustment for base station B is still the optimal 0 degree and thesecond best phase adjustment of 180 degrees from base station A isachieved.

FIG. 47 illustrates a transmission schedule 4700 for addressingsecond-priority interference from base station D according to anembodiment of the present invention. The scheduling process moves toprocess the priority 2 interference from base station D since there isno remaining blocks with priority 2 interference from base station C tobe scheduled. The optimal scheduling location for CPE #4 is on timeslot#1 on the frequency resources with a phase adjustment of 90 degrees frombase station A and a phase adjustment of 0 degree from base station D.Since there are already six blocks of data scheduled on those resourcesand there are only eight such resources available, only two of theblocks of data for CPE #4 can be sent on those resources. The remainingfour blocks are sent on timeslot #3 with the second best phaseadjustment from base station A of 180 degrees and a phase adjustment ofzero degree from base station D.

FIG. 48 illustrates a transmission schedule 4800 for addressing priority3 interference according to an embodiment of the present invention.There is only one priority 3 interference to process. The optimallocation for CPE #6 is with a phase adjustment of 180 degrees from basestation A. In this case there are two priority 3 interferencesources—from base station B and base station D. The scheduling processcan schedule the blocks for CPE #6 in timeslot #2, where theinterference from base station B will be reduced, or on timeslot #3where the interference from base station D will be reduced. Fourresource blocks are sent on timeslot #3 and two resource blocks are senton timeslot #2.

FIG. 49 illustrates a transmission schedule 4900 for addressing priority4 interference according to an embodiment of the present invention.There is one priority 4 to schedule, i.e., CPE #9. This CPE has thelowest priority level for scheduling. Since the best signal for this CPEis with a phase adjustment of 270 degrees from base station A, thescheduling process schedules transmissions to this CPE in the availabletime/frequency resources with the phase adjustment of 270 degrees.

The scheduling examples above describe how transmissions from basestation A to the CPEs are scheduled according to embodiments of thepresent invention. The scheduling of transmissions to CPEs served bybase stations B, C and D are scheduled in a similar manner. In somecases it may not be possible to match up all CPE transmissions with thebest, the second best, or the third best phase adjustment. In thosecases the CPE transmissions will be scheduled on timeslots #4 to #7,with optimal transmit phase adjustments from the serving base stations,but with no guarantees on the phase adjustments from any interferingbase stations.

While several embodiments of the present invention have been illustratedand described herein, many changes can be made without departing fromthe spirit and scope of the invention. Accordingly, the scope of theinvention is not limited by any disclosed embodiment. Instead, the scopeof the invention should be determined from the appended claims thatfollow.

What is claimed is:
 1. A computer implemented method for transmittingbeamformed data to a mobile station, the method comprising: receiving aquantized phase angle information of a reference signal from a mobilestation at a first base station that transmitted the reference signal tothe mobile station; selecting a first phase adjustment angle based onthe quantized phase angle information received from the mobile station;scheduling a first data package in a first wireless resource with thefirst phase adjustment at the first base station in coordination with anassociated second phase adjustment of a second wireless resource at thesecond base station; and transmitting a first beamformed signal that isprovided with the first phase adjustment angle based on the receivedquantized phase angle information to the mobile station from the firstbase station.
 2. The method of claim 1, wherein the quantized phaseangle information received is associated with one of eight quantizedphase angle zones, wherein the reference signal is a beamformed signal.3. The method of claim 1, wherein the quantized phase angle informationis received by the first base station from the mobile station in a formof three-bit information.
 4. The method of claim 1, wherein the firstbase station is a serving base station for the mobile station, and themobile station is receiving an interference signal from a second basestation, and wherein the first beamformed signal is transmitted to themobile station by the first base station as part of the first datapackage.
 5. The method of claim 4, further comprising: scheduling asecond data package in the second wireless resource with a third phaseadjustment at the first base station in coordination with the associatedsecond phase adjustment of the second wireless resource at the secondbase station; and scheduling a third data package in a third wirelessresource with a fourth phase adjustment at the first base station incoordination with the associated second phase adjustment of a secondwireless resource at the second base station, wherein the first phaseadjustment is the optimal phase angle correction, the third phaseadjustment is the second most optimal phase angle correction, and thefourth phase adjustment is the third most optimal phase anglecorrection.
 6. The method of claim 4, wherein the first wirelessresource at the first base station corresponds to a first timeslotassociated with at least one frequency, and wherein the second wirelessresource at the second base station corresponds to the first timeslotassociated with the at least one frequency of the first base station. 7.The method of claim 4, wherein the first phase adjustment is a quantizedphase adjustment that determines the amount of constructive interferencein the first beamformed signal as received by the mobile station; andwherein the second phase adjustment is a quantized phase adjustment thatdetermines the amount of destructive interference in the interferencesignal as received by the mobile station.
 8. The method of claim 4,wherein the first data package is transmitted in the first wirelessresource such that the second phase adjustment associated with theinterference signal transmitted by the second base station is selectedto cause the interference signal to be received as deconstructiveinterference at the mobile device.
 9. The method of claim 4, wherein thefirst phase adjustment and the second phase adjustment are associatedvia a first phase adjustment map associated with the first base stationand a second phase adjustment map associated with the second basestation, the first phase adjustment map and the second phase adjustmentmap aligning the first wireless resource and the first phase adjustmentwith the second wireless resource and the second phase adjustment. 10.The method of claim 1, wherein the quantized phase angle informationreceived is associated with one of eight quantized phase angle zones,and the first phase adjustment angle is associated with one of fourphase adjustment angles.
 11. The method of claim 10, wherein the fourphase adjustments angles are provided in 90 degree steps, and thereference signal is a beamformed signal.
 12. A computer implementedmethod for receiving beamformed data from a base station, the methodcomprising: receiving a first signal from a first base station at amobile station; measuring a first phase difference of the first signalat the mobile station; transmitting a quantized phase angle informationof the first signal based on the first phase difference measured by themobile station to a first base station that transmitted the first signalto the mobile station; and receiving a first beamformed signal that isprovided with a first phase adjustment angle from the first basestation, wherein the first phase adjustment angle is selected by thefirst base station based on the quantized phase angle informationtransmitted by the mobile station, wherein the first base station is aserving base station for the mobile station, and the mobile station isreceiving an interference signal from a second base station, wherein thefirst beamformed signal is transmitted to the mobile station by thefirst base station as part of a first data package, and wherein thefirst base station schedules the first data package in a first wirelessresource with the first phase adjustment in coordination with anassociated second phase adjustment of a second wireless resource at thesecond base station.
 13. The method of claim 12, wherein the quantizedphase angle information received is associated with one of eightquantized phase angle zones, and wherein the first signal is abeamformed signal.
 14. The method of claim 12, wherein the quantizedphase angle information is received by the first base station from themobile station in a form of three-bit information.
 15. The method ofclaim 12, wherein the quantized phase angle received is associated withone of eight quantized phase angle zones, and the first phase adjustmentangle is associated with one of four phase adjustment angles.
 16. Themethod of claim 12, wherein the four phase adjustments angles areprovided in 90 degree steps and the first signal is a beamformed signal.17. The method of claim 12, further comprising: receiving a second datapackage and a third data package from the first base station, whereinthe first base station schedules the second data package in a secondwireless resource with a third phase adjustment in coordination with theassociated second phase adjustment of a second wireless resource at thesecond base station, and wherein the first base station schedules thethird data package in a third wireless resource with a fourth phaseadjustment in coordination with the associated second phase adjustmentof a second wireless resource at the second base station, wherein thefirst phase adjustment is the optimal phase angle correction, the thirdphase adjustment is the second most optimal phase angle correction, andthe fourth phase adjustment is the third most optimal phase anglecorrection.
 18. The method of claim 12, wherein the first wirelessresource at the first base station corresponds to a first timeslotassociated with at least one frequency, and wherein the second wirelessresource at the second base station corresponds to the first timeslotassociated with the at least one frequency of the first base station.19. The method of claim 12, wherein the first phase adjustment is aquantized phase adjustment that determines the amount of constructiveinterference in the first beamformed signal as received by the mobilestation; and wherein the second phase adjustment is a quantized phaseadjustment that determines the amount of destructive interference in theinterference signal as received by the mobile station.
 20. The method ofclaim 12, wherein the first data package is transmitted in the firstwireless resource such that the second phase adjustment associated withthe interference signal transmitted by the second base station isselected to cause the interference signal to be received asdeconstructive interference at the mobile device.
 21. The method ofclaim 12, wherein the first phase adjustment and the second phaseadjustment are associated via a first phase adjustment map associatedwith the first base station and a second phase adjustment map associatedwith the second base station, the first phase adjustment map and thesecond phase adjustment map aligning the first wireless resource and thefirst phase adjustment with the second wireless resource and the secondphase adjustment.
 22. A wireless communication system provided at a basestation for coordinating the scheduling of beamformed data to reduceinterference, the system comprising: a processor; a receiver; and atransmitter, wherein the system is configured to: transmit a firstsignal to a mobile station, receive a quantized phase angle informationof the first signal from the mobile station, select a first phaseadjustment angle based on the received quantized phase angle informationfrom the mobile station, schedule a first data package in a firstwireless resource with the first phase adjustment at the first basestation in coordination with an associated second phase adjustment of asecond wireless resource at a second base station, and transmit a firstbeamformed signal that is provided with the first phase adjustment anglebased on the received quantized phase angle information to the mobilestation.
 23. A wireless communication system for coordinating thescheduling of beamformed data to reduce interference, the systemcomprising: a first base station; a second base station; a datacommunication network facilitating data communication amongst the firstbase station and the second base station; and a first mobile station,wherein a first beamformed signal received by the first mobile stationfrom the first base station is received as a communication, wherein asecond beamformed signal received by the first mobile station from thesecond base station is received as interference, and wherein the systemis configured to: transmit a first signal to a mobile station, receive aquantized phase angle information of the first signal from the mobilestation, select a first phase adjustment angle based on the receivedquantized phase angle information from the mobile station, schedule afirst data package in a first wireless resource with the first phaseadjustment at the first base station in coordination with an associatedsecond phase adjustment of a second wireless resource at the second basestation, and transmit a first beamformed signal that is provided withthe first phase adjustment angle based on the received quantized phaseangle information to the mobile station from the first base station.